1. Field of the Invention
The present invention relates to a differential for a motor vehicle.
More particularly, the differential of the invention comprises a housing through which axially extend two shafts driving the driving wheels of the vehicle, sun gears mounted in the housing coaxially with the shafts and rigid with the latter as concerns rotation, planet gears journalled in the housing to rotate about a shaft perpendicular to the shafts and fixed at its ends to the housing, these planet gears being cooperative with the sun gears.
2. Description of the Prior Art
It is known that this type of mechanism has a function of dividing in a judicious manner the driving torque between each of both left and right driving wheels of a vehicle so as to ensure a maximum amount of traction in th case of ground having slippery regions while permitting driving on an adhering road which is as precise and certain as with a conventional differential.
It is also known that a conventional differential equally divides the torrques between the two driving wheels, which constitutes a drawback of considerably reducing the traction when one of the driving wheels bears against a slippery surface of the ground.
Generally, the differentials having a limited slip or self-locking differentials employ the friction between the surfaces in permanent contact pertaining either to stacks of disks or to cones. It has the drawback of high instability of their corrective action which may result in zero efficiency or in a relative locking of the two wheels in an erratic and unforseeable manner. These drawbacks are mainly due to variations in the coefficients of sliding of the rubbing surfaces and variations in the sliding rate in the different stages of the meshing of the sun gears and planet gears of these differentials.
There is consequently a disturbance in the precision of the driving of the vehicle when the frictions are excessively high (bad road holding), since the resulting traction force may very distinctly shift from the left to the right of the vehicle and, when the friction is insufficient, there is an absence of traction when a wheel encounters ground without adherence.